1. Field of the Invention
The present invention relates to a wire electric discharge machine and an automatic programming device for a wire electric discharge machine that have an anti-drop function for a workpiece by attaching an electrode component to the workpiece.
2. Description of the Related Art
Descriptions are given to machining in a case of carrying out die machining with a wire electric discharge machine using FIG. 8 taken from above of a workpiece.
The machining starts from a machining start hole 15 with a wire electric discharge machine. In a machining path through which a wire electrode 13 has gone, a machining groove 14 is formed. In a die machining method in prior art, in a case of carrying out machining to produce a core 12 using a wire electric discharge machine, a residual stock removal 11 is generally provided in a workpiece base material 10 during rough machining and the core 12 is cut off during a post treatment.
Therefore, an operator has to stay on the wire electric discharge machine for the core cutoff machining, and also it takes extra time for machining for the number of cores 12. In the cutoff machining in prior art, there are possibilities of: (a) disconnecting the wire electrode 13 by the core 12 to be cut off which makes contact with the wire electrode 13; (b) damaging both the core 12 and the workpiece base material 10 due to development of concentration of local electric discharge before short circuit of the wire electrode 13 and the workpiece base material 10 via the core 12 to be cut off and drop; and (c) breaking a nozzle, such as fracturing or cracking a lower nozzle with the dropping core, so that they become a burden on the operator.
FIGS. 9A through 9C are diagrams to illustrate problems that occur upon cutting off a core during die machining in prior art.
FIG. 9A illustrates that there is a possibility of disconnecting a wire electrode 26 by a core 20 that is cut off making contact with the wire electrode 26, where the reference numeral 21 denotes an area in which the wire electrode is disconnected by the machining to cut off the core 20. FIG. 9B illustrates that there is a possibility of breaking a nozzle, such as fracturing or cracking a lower nozzle with the dropping core, where the reference numeral 23 denotes an area in which the core breaks a lower nozzle due to the cutoff machining. FIG. 9C illustrates that there is a possibility of damaging both the core and a workpiece base material 24 due to development of concentration of local electric discharge before short circuit of the wire electrode 26 and the workpiece base material 24 via the core to be cut off and drop, where the reference numeral 25 denotes an area in which the core makes contact with the workpiece base material due to the cutoff machining.
With that, in order to prevent movement of a workpiece during machining with a wire electric discharge machine and to prevent drop of a core at the time of finishing the machining, a technique making use of phenomenon that electrode component particles are attached to the workpiece base material is known. Techniques to fix a core and a workpiece base material by depositing attachments in a machining groove of the workpiece are known as follows.
Japanese Patent Application Laid-Open No. 57-96724 discloses a technique that, in wirecut electric discharge machining that produces a core, a workpiece base material and a core are bonded by depositing attachments in a machining groove between the core and the workpiece base material, thereby holding the core with the workpiece base material during the machining.
FIG. 10 is a diagram to illustrate a workpiece base material having a core in a thin rib or pectinate shape machined therein.
Electric discharge machining is carried out in a workpiece base material 31 from a machining start hole 15 along a machining path and attachments 35 containing brass of the wire electrode are attached and deposited along the machining groove formed in the machining path. A core 30 has an area 30a in a thin rib or pectinate shape of the core. The workpiece base material 31 has an area 31a in a thin rib or pectinate shape of the workpiece base material 31. By the attachments 35 attached and deposited along the machining groove, the core 30 is held in the workpiece base material 31.
In addition, Japanese Patent Application Laid-Open No. 62-218024 discloses a technique to prevent drop of a machined object by attaching an electrode component to an arbitrary part of a machining groove, and the attachment of the electrode component occurs at a desired point of the machining groove along a slight distance.
However, in Japanese Patent Application Laid-Open No. 57-96724 above, it is described to hold the core with the workpiece base material by depositing the attachments all around the machining groove from a machining start time to a machining end time. Accordingly, with this technique, it becomes difficult to strike off the core after electric discharge machining because the core and the workpiece base material are firmly bonded by the attachments containing brass of the wire electrode that are deposited all around the machining groove.
Therefore, when trying to strike off a core forcibly, a variety of problems are prone to occur, such as, in a case of a small core, that there is a possibility of damaging a workpiece base material by hitting the workpiece base material by mistake, that there is a possibility of hitting many times because a core does not easily fall, thereby damaging a workpiece base material due to misalignment of the core, and that there is a possibility of hitting many times because a core does not easily fall, thereby disabling later machining due to misalignment of a workpiece base material fixed to a table and, in a case of a core in a shape, such as a thin rib or pectinate shape, that there is a possibility of breaking off the ribs or the pectinate portion.
FIGS. 11A through 11E are diagrams to illustrate a variety of problems that possibly occur upon striking off a core from a workpiece base material after depositing attachments all around a machining groove by the prior art techniques.
As illustrated in FIG. 11A, when the attachments 35 are deposited all around the core 30 (all around the machining groove), it becomes difficult to strike off the core 30. When trying to strike off the core 30, as illustrated in FIG. 11B, there is a possibility of misaligning a position of the core 30 and so damaging the workpiece base material 31 and, as illustrated in FIG. 11C, there is also a possibility of misaligning a position of the workpiece base material 31. Further, as illustrated in FIG. 11D, when using a hammer 37 to strike off the core from the workpiece base material 31, there is also a possibility of damaging the workpiece base material 31 by hitting the workpiece base material 31 by mistake, not the core 30, with the hammer 37. In addition, as illustrated in FIG. 11E, in such a case that the workpiece base material 31 after machining has an area 31a in a thin rib or pectinate shape, there is a possibility of bending the workpiece base material 31.
The technique disclosed in Japanese Patent Application Laid-Open No. 62-218024 described above is to prevent drop of a machined object by attaching an electrode component to an arbitrary part of a machining groove, and the attachment phenomenon occurs at a desired point of the machining groove only along a slight distance. However, this technique is to attach an electrode component in an arbitrary part of the machining groove only along a slight distance, and the electrode component is not always attached by an amount necessary to hold the core with the workpiece base material. For example, there is a possibility that the core falls from the workpiece base material during machining due to a too small number of specified attachment places, while in contrast, there is also a possibility that it becomes difficult to strike off the core from the workpiece base material due to a too large number of specified attachment places.